What you’re looking at above are fulgurites, natural hollow glass tubes formed in quartzose sand, silica, or soil by lightning strikes. They are formed when lightning with a temperature of at least 1,800 °C (3,270 °F) instantaneously melts silica on a conductive surface and fuses grains together; the fulgurite tube is the cooled product. Continue reading for more fun and interesting things you probably didn’t know were true.